Cathode ray tube video displays have been the standard for many years. Cathode ray tube displays create images by selectively firing of a cathode ray or electron beam on a surface coated with an illuminating material, the surface illuminating in response to the electron beam. With this technology, however, a minimum distance between the source of the electron beam and the surface coated with illuminating material was required in order to properly control the electron beam to produce a desired image. In most cases, the cathode ray was fired substantially perpendicularly to the display screen. Therefore, displays using this technology typically required a minimum distance between the viewing surface of the display screen and the electron gun behind the display screen. Further, the technology has been criticized for emitting potentially damaging amounts of radiation from the cathode ray tube display surface.
In many applications it has been desirable to employ video displays with shorter front to back dimensions. Lap top computers, for example, require thin video displays to create a computer package of a minimal volume. One way to create a thinner video display was to discharge the cathode rays from directions that were not perpendicular to the display screen. However, when cathode rays were fired from these positions, the control of the cathode rays was much more difficult and resulted in the degradation of the video image.
A solution that overcame these problems included selectively energizing specific display locations using an electrical signal. In this arrangement, a display screen was provided with discrete pixels of illuminating material or another material with an alterable appearance. Arranged on the display screens were a plurality of electrically conductive row traces and a plurality of electrically conductive column traces, each row and column trace extending across the screen only once. Typically, the row traces were disposed perpendicularly to the column traces. The pixels were arranged such that energizing a particular row and a particular column caused a specific pixel to illuminate. Therefore, each pixel on the display screen could be uniquely addressed by energizing a certain row and column combination.
This technology, however, required a driver for each row trace and for each column trace. In a system with one thousand rows of resolution and one thousand columns of resolution, 2000 drivers were required. Typically, only one pixel was addressed at a time requiring the individual enablement of a specific row driver and a specific column driver. In operation, an incoming video signal was converted and decoded so that the pixels could be selectively activated. However, with this technology, the required signal decoding and selective enablement of a specific row driver and a specific column driver could not be performed quickly enough to drive high resolution displays. The cost of such displays was great because of the large number of drivers required. Further, these displays were not efficient and, in a typical portable computer installation, consumed a large percentage of the available energy.